1. Technical Field
The present disclosure relates to an imaging device and a signal processing method.
2. Related Art
Recently, as the resolution of a solid-state imaging element such as a charge coupled device (CCD) image sensor and a complementary metal oxide semiconductor (CMOS) image sensor becomes higher, a demand for an information device having a photographing function such as a digital still camera, a digital video camera, a cellular phone such as a smart phone, and a personal digital assistant (PDA) is rapidly increasing. Further, the information device having an imaging function as described above is referred to as an imaging device.
In such an imaging device, as a focus control method which focuses on a major subject, a contrast auto focus (AF) method or a phase difference AF method is employed. Since the phase difference AF method may detect a focusing position with high precision at a high speed as compared with the contrast AF method, the phase difference AF method is widely employed in various imaging devices.
For example, Patent Literature 1 (JP-A-2010-286826) discloses an imaging device which has some of the pixel cells included in an imaging element as a phase difference detecting pixel cell and performs the phase difference AF using a signal read out from the phase difference detecting pixel cell.
The imaging device disclosed in Patent Literature 1 performs shading correction which predicts shadings of a subject image (image A) obtained by being captured by one of a pair of phase difference detecting pixel cells and a subject image (image B) obtained by being captured by the other one of the pair of phase difference detecting pixel cells from lens information, ranging point information, and latest defocus information to adjust a light quantity ratio of the image A and the image B, thereby improving precision of the phase difference AF.
Further, even though it is not a technique of phase difference AF, Patent Literature 2 (JP-A-2009-159093) discloses a lens switching imaging device which uses a live-view image to calculate a shading correction coefficient, as a shading correcting technique.